1. Field of the Invention
The present invention relates to a variable magnification optical system and an optical apparatus having the same, and more particularly, to a variable magnification optical system having an image stabilizing function, which is suitable for use in a video camera, a silver-halide photographic camera, an electronic still camera, etc., and which is capable of stabilizing a photographed image by moving a lens unit that is a part of the variable magnification optical system in such a way as to have a component having directions perpendicular to an optical axis to optically correct shaking of the photographed image obtained when the variable magnification optical system vibrates (tilts), so as to obtain a stationary image.
2. Description of Related Art
Heretofore, there have been proposed a variety of image-stabilizing optical systems having the function of preventing shaking of a photographed image due to the vibration of each optical system.
For example, in an image-stabilizing optical system disclosed in Japanese Laid-Open Patent Application No. Sho 56-21133, in response to an output signal of a detection means for detecting the vibration state of the optical system, an optical member that is a part of the optical system is moved in such a direction as to cancel the vibratory displacement of an image due to the vibration of the optical system, thereby stabilizing an image.
In a photographic system disclosed in Japanese Laid-Open Patent Application No. Sho 61-223819 (corresponding to U.S. Pat. No. 4,927,250), in which a variable angle prism is disposed on the most object side, the apex angle of the variable angle prism is varied in correspondence with the vibration of the photographic system, thereby stabilizing an image.
In photographic systems disclosed in Japanese Laid-Open Patent Application No. Hei 1-116619 (corresponding to U.S. Pat. No. 5,270,857) and Japanese Laid-Open Patent Application No. Hei 2-124521 (corresponding to U.S. Pat. No. 5,039,211), the vibration of the photographic system is detected by utilizing an acceleration sensor or the like, and, in response to an output signal of the acceleration sensor or the like, a lens unit that is a part of the photographic system is moved in directions perpendicular to an optical axis, thereby obtaining a stationary image.
In addition, in a variable magnification optical system disclosed in Japanese Laid-Open Patent Application No. Hei 7-128619, which has the four-unit structure having positive, negative, positive and positive lens units, the third lens unit being composed of two, positive and negative, lens subunits, the positive lens subunit of the third lens unit is moved in directions perpendicular to an optical axis to stabilize an image.
Further, in a variable magnification optical system disclosed in Japanese Laid-Open Patent Application No. Hei 7-199124 (corresponding to U.S. Pat. No. 5,585,966), which has the four-unit structure having positive, negative, positive and positive lens units, the whole third lens unit is moved in directions perpendicular to an optical axis to stabilize an image.
On the other hand, in Japanese Laid-Open Patent Application No. Hei 8-5913 (corresponding to U.S. Pat. No. 5,847,882 and U.S. Pat. No. 6,094,312), there is disclosed a variable magnification optical system having the five-unit structure having positive, negative, positive, positive and negative lens units, in which the variation of magnification is performed by moving the second and fourth lens units, thereby attaining the reduction of the diameter of a front lens member.
Further, in Japanese Laid-Open Patent Application No. Hei 10-197786, there is disclosed a variable magnification optical system having the five-unit structure having positive, negative, positive, negative and positive lens units, in which the fourth lens unit is moved in directions perpendicular to an optical axis to stabilize an image.
However, among the above-mentioned variable magnification optical systems having the image stabilizing function, optical systems each having a zoom ratio of 8 or more, although being adaptable for video cameras or the like, are insufficient for being used with electronic still cameras each having 1,000,000 pixels or more, in terms of the correction of aberration.
It is an object of the invention to provide a variable magnification optical system having an image stabilizing function, which, while securing a zoom ratio to a given degree or more, is corrected well for aberration to such a degree that the variable magnification optical system is usable, for example, as a photographic system of an electronic still camera using an image sensor having 1,000,000 pixels or more.
To attain the above object, in accordance with an aspect of the invention, there is provided a variable magnification optical system, which comprises, in order from an object side to an image side, a first lens unit of positive optical power, a second lens unit of negative optical power, a third lens unit of positive optical power, a fourth lens unit of negative optical power and a fifth lens unit of positive optical power. At least the second lens unit and the fourth lens unit are moved along an optical axis during a variation of magnification, and the third lens unit is moved in such a way as to have a component having directions perpendicular to the optical axis to displace an image formed by the variable magnification optical system.
In accordance with another aspect of the invention, there is provided an optical apparatus, which comprises the variable magnification optical system according to the above-mentioned aspect.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.